Lower hydrocarbons such as methane, ethane, propane, n-butane, and isobutane are often found in crude petroleum, and are also present in natural gas streams. Water is also among the components typically present in petroleum-bearing formations. Under conditions of elevated pressure and reduced temperature, mixtures of water and many lower hydrocarbons tend to form hydrocarbon hydrates known as clathrates. Such hydrates are crystalline structures in which water has formed a cage structure around a guest molecule such as the lower hydrocarbon. For example, at a pressure of about 1 MPa, ethane can form gas hydrates with water at temperatures below 4° C.; at a pressure of 3 MPa, it can form gas hydrates with water at temperatures below 14° C. Temperatures and pressures such as these are commonly encountered for many environments in which natural gas and crude petroleum are produced and transported.
Gas hydrates are of particular interest owing to the pipeline blockages that can be produced during the production and transport of natural gas or crude petroleum. As gas hydrates form and grow inside a pipe or conduit, they can block or damage the pipeline and associated valves and other equipment. Prevention or inhibition of gas hydrate formation and agglomeration is thus sought in order to minimize unscheduled shutdowns, maintenance and repair, and to provide safer operation of production and/or transport facilities.